You might find that the filter inside the separator clogs after awhile. If so, I removed it and just use the housing as a catch can. It seems to work fine that way.
I did'nt buy one, i bought one of those oil separators from Jegs, [looks like a minature separator off a compressor] and i have about a quarter of a teaspoon [if that] after a 100 miles of use. The problem with mine is the Cobra intake, it only has a tiny oil baffle compared to the stock, a modified baffle was available from Ford that goes full length, but the parts now deleted.
The 4th link down shows the pattern to make one, obviously not everyone sucking oil out of the pcv is caused by this.